1. Field of the Invention
The present invention relates to a laser treatment apparatus for use in an ophthalmic operation on an eye to be treated by a laser beam, the apparatus using a slit-lamp as an observing optical system, and more particularly to a laser treatment apparatus which comprises a safety mechanism to prevent wrong irradiation of a laser beam.
2. Description of Related Art
Laser treatment apparatus for performing opthalmic operations, in which a laser beam irradiates the affected part of a patient's eye suffering from retinal detachment, for example, then photocoagulating on the irradiated affected part, are known.
Various systems for observing the direction of the transmitted laser beam to the affected part of the eye to be treated, have been proposed. Such proposed observing sytems are selected for use depending on the the condition of the patient, the part of the eye which is affected, and the type of laser to be used. An apparatus using a slit-lamp microscope as an observing optical system is known. This apparatus may allow an attending oculist to stereoscopically observe the patient's eye, and, in particular, it may be used to conduct precise photocoagulation on the affected part of the posterior pole of the eye.
A laser treatment apparatus using a slit-lamp microscope as an observing system is provided with an optical system to transmit or direct a laser beam into an observing optical path of the slit-lamp microscope and a protection device to protect an eye of the oculist from laser beams reflected by lenses and the patient's eye. The protection device has a protection filter for the oculist, which is constructed so as to be located out of the optical path of the observing system to provide sufficient brightness to the oculist during observation and to be moved into the optical path in accordance with trigger signals of laser irradiation.
However, it is difficult to attach reflecting mirrors to direct a laser beam and removably attach a protection filter to a conventional slit-lamp without substantial modification, while there may be no particular difficulty in designing the slit-lamp microscope as a simple purpose device of a laser treatment apparatus.
If the conventional slit-lamp microscope is provided with the reflecting mirrors and a removable protection filter, then a sufficient working distance between the slit-lamp microscope and the patient's eye can not be obtained.
Further, to obtain a sufficient working distance, the protect filter must be fixedly located on the optical path of the slit-lamp microscope. When the protection filter is so fixedly located on the optical path, a part of an observation light beam is eclipsed by the protection filter even when laser treatment operation is not carried out, as a result, the patient's eye can not be observed adequately.
In a slit-lamp microscope having no protection filter, if a switch for laser irradiation is turned on by mistake, a laser beam as projected will be transmitted to the oculist's eye, therefore causing a problem of lack of safety.